Lithographic press dampening mechanism for spraying desensitizing liquid on lithographic plates



Sept. 23, 1958 J. o. SANKER 2,853,004

LITHOGRAPHIC PRESS DAMPENING MECHANISM FOR SPRAYING DESENSITIZING LIQUIDON LITHOGRAPHIC PLATES Filed April 19, 1955 INVENTOR. Ja/W Q 54/7/(516BY M ATTORNEYS.

United States Patent Ofifice LITHOGRAPHIC PRESS DAMPENING MECHA- NISMFOR SPRAYING DESENSITIZING LIQ- UID ON LITHOGRAPHIC PLATES John O.Sanker, Cincinnati, Ohio Application April 19, 1955, Serial No. 502,461

3 Claims. (Cl. 101-148) My invention relates to lithographic presses andto apparatus and a method for spraying desensitizing fluid onto theprinting plates of said presses.

It is normal in lithographic press construction to have a rotatablecylinder which carries the printing or lithographic plates and Since theplates require etching, to arrange what are called dampening or dampingrollers in peripheral contact with the plates to apply a film ofdesensitizing fluid from the surface of the dampening rollers to thesurface of the plate.

These presses run at very high speeds and normally the fabric surfacesof the dampening rollers pick up spots of ink from the plates. These inkspots gradually increase in size and as a final result do not apply aneven coating of desensitizing fluid. This causes ink to adhere tounetched areas of the lithographic plate and the printed impressionbecomes smudged and an inferior quality of lithographic reproductionresults.

It is the object of my invention to keep the dampening rollers clean bymounting them so that they are spaced from peripheral contact with thelithographic plates and by a novel method to cause the desensitizingfiuid to be ejected in a fine spray against the plates. This Iaccomplish by forming the dampening rollers with the peripheral surfacesformed by a series of radially projecting fibers or nap. This nap issimilar to certain grades of carpeting particularly nylon carpeting.

It is my object to provide a bar bearing against the nap of thedampening roller to bend down the nap as it passes under the bar. Afteremerging from contact with the bar the fibers spring back to theirnormal radial arrangement and in this snapping back of the individualfibers there is ejected a fine spray of liquid against the printingplate.

As the surface of the cylinder passes the dampening rollers there arecertain arcs of the cylinders which do not require a film ofdesensitizing fluid and accordingly I avoid spraying at this position bymoving the spray bars out of contact with the nap of the dampeningrollers. This can be readily accomplished by a cam action.

The foregoing objects and other objects to which I will refer in theensuing description, I accomplish by that certain combination andarrangement of parts of which I have shown one typical arrangement.

In the drawings:

Figure 1 is a diagrammatic sectional view of the printing rollers,inking rollers and dampening roller mechanism of a lithographic press.

Figure 2 is an enlarged sectional view showing details of the dampeningrollers.

As shown in Figure 1, the press cylinder 1 is mounted on a rotatableshaft 2 and carries a lithographic plate 3 bolted into position on thecylinder. The cylinder has recessed portions 4, 5, and normally isbolted at one end as with fixed bolts 6. The other end is adjustable bymeans of a clamp 7 which secures the end of the plate and has a threadedadjustment screw 8 held in position by lock nuts 9.

2,853,004 Patented Sept. 23, 1958 Between the recessed portions theremay be an inking plate 10 which, during rotation of the cylinder, bearsagainst the ink distributing rollers 11 smoothing out the films of inkcarried by the rollers so that the ink will be applied in an even coatto the design areas of the plate.

The dampening mechanism consists of a pan or tank 12 within which ametal roller 13 revolves carrying up with it a film of desensitizingsolution from the pan. A doctor roll 14 is mounted on a rocker 15 whichalternately moves the roll 14 into peripheral contact with the roll 13and then moves it into peripheral contact with the distributing roll 16.

It was to the metallurgical composition. of the roll 16 that myinvention as set forth in my Patent 1,612,061 granted December 28, 1926related. The distributing roller 16 is in constant peripheral contactwith the dampening rollers 17, 17a.

Referring to the enlarged Figure 2, the surface of the dampening rollers17, 17a, is covered with radially extending fibers 18, 1811. Thesefibers, when they pass under the spray bars 19, 19a, are bent down asindicated at 20, 20a. As soon as they pass along out of contact with thebars 19, 1911, they spring back to their radially erect position andduring this movement eject or snap fine particles of desensitizingsolution onto the plate.

The spray bars 19, 19a are mounted on lever arms 21, 21a which areactuated by a link 22 and adjustment rod 23 connected to a pivoted crank24. The pivoted crank is connected to a link 25 which is adjustable andcarries a cam wheel 27 carried by the shaft 2.

It will be noted that the mechanical arrangement illustrated for movingthe spray bars 19, 19a out of contact with the nap surfaces of thedampening rollers 17, 17a is primarily diagrammatic and is merely onearrangement for inhibiting the spray controlling effect of the spraybars. Other arrangements may be used to accomplish this same result.

The method which I have discovered. for flattening down the nap of thedampening rollers and permitting the nap to spring back ejecting a finespray against the plates is new as far as I am advised.

As I have explained, the complete avoidance of smudging the dampeningrollers with splotches of ink and the consequent avoidance of smudgingof the lithographic design on the printed sheet brings about animportant improvement in the clean cut printing of the plate.

The inhibiting of the spray distributing operation, as for example whenthe inking plate 10 is passing by the dampening rollers, may beaccurately controlled to avoid depositing the desensitizing solution onthe cylinder in the areas where the solution would cause damagingresults.

I have further found that by my new spraying arrangement I can depositthe desensitizing solution in a more uniform film on the lithographicplate.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. In a lithographic press the combination of a rotatable cylindercarrying a printing plate and which plate requires the applicationthereto of desensitizing solution, a supply receptacle for desensitizingsolution, a metal roller fed by emergence in the desensitizing solution,a doctor roller mounted to engage said metal roller, a distributingroller adapted to receive a film of desensitizing solution from saiddoctor roller and a dampening roller provided with means for rotatingthe same, said dampening roller composed of radially extending fibers,said metal roller, doctor roller, distributing roller and dampeningroller being operable as a unit independent of said rotatable cylinderand means for bending over said fibers and releasing them to cause themto spray desensitizing fluid onto the plate, and means for inhibitingthe action of said fiber bendingwover and releasing means timed forintermittent action with the rotatable cylinder mechanism to inhibitspraying at predetermined intervals of cylinder rotation.

v2. In .a lithographic press the combination of a rotatable cylindercarrying a printing plate and whichplate requires the applicationthereto of desensitizing solution, a supply receptacle for desensitizingvsolution, a ,rnetal roller fed by emergence in the desensitizingsolution, a doctor roller mounted to engage saidrnetal roller, adistributing roller adapted to receive a vfilm of desensitizing solutionfrom said doctor roller and a dampening roller provided with means forrotating the same, said dampening roller composed .ofradiallyextendingfibers, said metal roller, doctor roller, .distributingrollerand dampening roller being operable as a unit independent of saidrotatable cylinder, and means. for bending voversaid.fibers andreleasing them to causethem to spray desensitizing fluid onto the plate,andmeans for inhibiting the action of ,saidfiber bending over andreleasing means timed vfor intermittent action with the rotatablecylinder mechanism to inhibit spraying at predetermined intervals ofcylinder rotation, said means for bending over and releasing the fiberscomprising a'bar normally bearing against side fibers.

3. In the combination of parts as recited in claim 1 wherein anadditional dampening roller is arranged to operate in series with theone dampening roller for spraying onto a difierent area of'the rotatablecylinder.

References Cited in the file of this patent UNITED STATES PATENTS

